good evening, steve. >> reporter: janelle, thanks. good evening from a suddenly blustery cold denver, where the gold tonight is political substance. when this debate gets started in less than an hour here at the university of denver, moderator jim lehrer will demand the studio audience not boo or hiss or applaud. no distractions, he'll say. so the voters, many, many millions watching from home, will get to concentrate on what these political competitors have to say. more than 60 million americans could watch tonight's debate. >> i've made up my mind. but i'd still like to see both of the candidates sweat a little bit. >> reporter: president obama looked relaxed this week. mitt romney too, but he knows he has to change perceptions tonight. more voters now see romney negatively than see him positively. and that loses elections. >> only two presidential candidates in the last 20 years of "the wall street journal"/nbc polling have had a net negative image at this point and one of them lost, george h.w. bush. and romney needs to improve th